Dry eye disease is one of the most prevalent ophthalmic conditions affecting individuals over the age of 45 years, with over 12 million Americans suffering from dry eye. In addition, dry eye disease is two to three times more common in women, particularly as they age. There has been significant speculation and controversy that the normal sex hormone changes occurring during menopause increase the risk of dry eye disease in women. We propose to examine the association between three components relevant to the dry eye disease process: meibomian gland structure, output (lipid profile), and function (tear film stability). As postmenopausal women are at risk for dry eye disease, we propose to conduct a cross-sectional study of 434 age-matched postmenopausal women with and without dry eye disease with the following Specific Aims: 1. To test the hypothesis that postmenopausal women with dry eye have abnormal lipid molecular profiles using electro spray time-of-flight mass spectrometry, 2. To test the hypothesis that dry eye in post menopause is associated with increased tear film thinning rates measured with wavelength-dependent interferometry, and therefore, decreased tear film stability and 3. To test the hypothesis that anatomical gland changes indicative of previous and/or active disease can be seen with higher frequency in postmenopausal women with dry eye (Infrared video meibography and detailed classification and grading of meibomian gland disease. The long term goals of this research are to gain insight to the etiology of dry eye disease in women, which may yield potential avenues for therapeutic development. In addition, increased understanding of the disorder and appropriate management will increase patient quality of life and decrease the economic burden due to this chronic disorder. The National Eye Institute's National Plan for Eye and Vision Research has identified a need for clinical and basic research in the area of lachrymal gland and tear film physiology. Specifically stated, "With respect to the goal of translating discoveries into the prevention and treatment of ocular surface disorders: (the Institution promotes research to) gain an understanding of the epidemiology of and risk factors for infectious and inflammatory corneal and ocular surface diseases to develop preventive strategies." This project is a unique blend of interdisciplinary clinical and basic research, which may lead to the translation of findings to clinical care in dry eye disease.